5.0MX5

Just a FYI in case anyone's looking. 89 Thunderbird Rear End Differential Carrier 8 8 | eBay

My 8.8 has always made noise and now that I have the car back on the road, I'm debating pulling and trying to fix, or just do a change out. Anyway, found the above unit with 6 days left on the auction. Bummer for me is the seller doesn't want to ship.

If I knew what I'd be getting into, I'd do the repair, but with the unknown factor of can I fix it or not, I'm leaning toward just swapping for a (hopefully) good unit.

tbone heller

The most common noise problem in these units is the result of over-torquing the pinion nut after a pinion seal replacement.

5.0MX5

tbone, I've been doing what I can to make the car a nice, quite cruiser and as I quieten things down, the remaining noises become just that much more noticeable. The rearend's 30mph and up whine particularly so. It's constant above 30 both on cruise and light acceleration and coast mode. To me that means a bad bearing since loading the ring gear lightly doesn't cause a noise change (or at least not much if any).

If the noise is a bearing, anyway to tell if it's a pinon or carrier? If pinion related can the bearing be changed by just pulling the yoke and seal (hopefully). Also to be the eternal optimist, if the nut's just over-torqued, what's the procedure to correct. My first thought is you back it off, then torque to some listed value, but Life's taught me that if it seems simple or easy, it's usually not.

tbone heller

Over-torquing of the pinion nut will result in excess compression of the crush sleeve, a collapsible, ONE-TIME-USE, spacer that goes between the front & rear pinion bearings. By doing so, the bearings are over preloaded causing them to fail. The carrier will need to be removed for repair. I would suggest replacing ALL of the bearings & seals, & be done with it. If you do not have experience doing this type of work, I strongly suggest that you seek out a professional. Ask the parts counter guy at the Ford dealer (while you are there buying some friction modifier) if the "differential guy" does any work on the side. I used to charge around $100 cash to do that type of stuff. Remember that the cost of the fluid is high. It will cost you around $60 every time you go back into it to "fix" something.

5.0MX5

"crush sleeve, a collapsible, ONE-TIME-USE" I was afraid that'd be the case. And while I have a dial indicator, mics and calipers and a small ability to use, I'd gladly pay $100ish to make sure it was set up properly. Friction modifier, I've been using the Mopar supplement, seems to work Ok in the Ford unit.

Thanks for taking time to help.

RR

charchri4

Tom I thought if you used synthetic oil you did not need the fancy friction modifier. True? I have run many miles and many tracks without it and have not had a problem but I may be lucky.

For what it’s worth I have set up a dozen GM 7.5 rear ends and never had a problem but I’ll be damned if I can get this blasted 8.8 Ford quiet. Even a GM set up I did with used gears that had already been set up in 2 different housings were quieter than this mess. I’m about ready to start from scratch too so if you get bored in retirement and want to build me one let me know!

Ronnie $125 for a 3.27 8.8 is not a bad price but not breath taking either. It would cost a good 50 bucks to ship and I bet you can find one local for that. Have you looked on car-part.com or some of the other salvage sites? I paid $110 for mine shipped and had I not changed gears and rebuilt it it probably would have been quiet.

tbone heller

Ford recommends using the friction modifier in conjunction with their synthetic fluid. They recommend running the 75W140 synthetic fluid.